144 DKEDGINGS OF THE MARINE BIOLOGICAL ASSOCIATION : 



M. 14j. S. 24° W. Edd., 20 miles. 



Almost black, a very compact rock with sub-conchoidal fracture, 

 and lustre somewhat like a quartzite. The worn surface shows rather 

 minute banded structure. 



The same banded structure shows in section when examined by the 

 unaided eye, but is less prominent under the microscope ; this is a 

 sedimentary rock altered by contact metamorphism. The general 

 ground-mass is a crypto-crystalline substance, rising to a minute 

 mosaic here and there, and probably having a complex mineral com- 

 position. Felspar almost certainly plays an important part. In this 

 there occur small grey-clouded areas, presenting sections which are 

 chiefly of somewhat ill-defined rhombus shape, and which in certain 

 positions completely extinguish. One such area has a portion clear of 

 dusty products, and this shows high double refraction in a bright and 

 pure colour ; other similar instances occur. The dusty material shows 

 a tendency to arrange itself in zones and crosses, and from examina- 

 tion of a great number of these imperfect crystals there can be no doubt 

 that the rock is crowded with andalusite in a condition bordering on the 

 chiastolite form. For the rest, there is much small brown mica, and 

 titanic iron ore, mostly in very small grains, is quite plentiful. Such 

 a rock might easily arise from the metamorpliism of a Devonian or 

 Carboniferous slate by contact with a large boss of igneous material. 



Altered slates, having the appearance of being baked by proximity to 

 igneous rock, were also taken at tlie following stations, but have not 

 been examined microscopically. 



M. 11, M. 34, M. 72, M. 14, M. 15, M. 21 (common), M. 24 (very common), 

 M. 17, M. 18. 



LIMESTONE. 



M. 26b. S. 20° W. Edd., 18-4 miles. 



A blue-grey limestone, veined and mottled with lighter calcite, nnicli 

 like some of the South Devon middle Devonian series. Consists 

 almost entirely of irregular interosculating calcite patches, traversed 

 by cracks filled with clear calcite. The calcite forms give indication of 

 former organic remains, and at three places undoubted sections of 

 madrepore occur. Around and between the boundaries of some of the 

 calcite areas are very irregular and much folded lines of a granular 

 black substance, apparently carbonaceous. 



NEW RED SANDSTONE. 



CONGLOMERATE. 

 354/3b. Hand Deeps. 



A red conglomerate, certainly of the New Ked Sandstone period. 

 Among the derived constituents are quartz grains of some size 



